Method for sharpening knives and a knife-sharpening machine



Oct. 9, 1956 a. DE'VOR 2,765,591

METHOD FOR SHARPENING KNIVES AND A KNIFE-SHARPENING MACHINE Filed March 30, 1954 2 Sheets-Sheet 1 INVENTOR. GIJSBERT DE VoR ATTr) P/VE) 0st. 9, 1956 G. DE voR' 2,765,591

METHOD FOR SHARPENING KNIVES AND A KNIFE-SHARPENING MACHINE Filed March 50, 1954 2 Sheets-Sheet 2 INVENTOR. G/JSBERT DE Vole Arm/W5) 2,765,591 METHOD FOR SHARPENING KNIVES AND A KNWESPENDIG MAQHENE Gijsbert de Vor, Nieuw-Loosdrecht, Netherlands, assignor to N. V. Verus, (Zuracao, Netherlands Antiiles, a corporation of the Netherlands Application March 30, 195 Serial No. 419,835 6 Claims. (Cl. 51-102) The present invention relates to a method for sharpening knives the blades of which have a cross-section varying in their longitudinal direction and to a sharpening machine for use in said method.

By means of the conventional knife-sharpening machines it is possible to grind the face of the cutting edge on either side of a knife, but when long knives having sharp points and cutting edge faces of varying width are to be sharpened great skill and care are required to obtain satisfactory results while the operator, who constantly runs the risk of hurting his hands, should preferably be ambidextrous especially if the cutting edge faces on either side of the blade are to be identical.

The method and the machine according to this invention eliminate these disadvantages and enable anyone to correctly sharpen knives and scissors, and even to grind knives and scissors hollow.

According to the invention the method of hand sharpening knives and scissors on a rotating grinding disc, the blades of which knives or scissors have a cross-section varying in their longitudinal direction is characterized in that a machine comprising a movable system of blade supporting means is used, the rate of movement of said system in the plane containing the grinding disc being so high relative to the rate of movement of the knife that at each momentary place of contact between the blade and the grinding disc the location of said blade is adapted to the shape of its cross-section.

The sharpening machine for use in the above method is characterized in that it comprises a manually movable system of blade supporting means, which system admits of being moved at the required rate.

Said machine preferably comprises two oppositely rotatable co-planar grinding discs, while at least one blade supporting means is mounted for symmetrical movement relative to said grinding discs.

According to another feature of the machine the system of blade supporting means comprises two supports for the back of a blade and two supports for the cutting edge of a blade, the arrangement being such that the supports for the back and/ or for the cutting edge of a blade may fiank a grinding disc.

The provision of said two supports for the back of a blade offers the advantage that a three point support of a blade to be sharpened is obtained, said three points comprising the two points of support of the back of the blade on the two supports for said back and the point of contact between the blade and the grinding disc. The direction of rotation of said disc being towards the back of the blade, the grinding force exerted by said disc will firmly urge the blade against the supports for the back thereof whereby a high degree of stability is obtained. If the face of the cutting edge has been ground to the desired extent the supports for the cutting edge will take over the supporting function of the grinding disc and the blade may then be drawn on along the grinding disc. The entire grinding operation takes a short time only and does not require any skill. The blade supporting mean-s automatically determine the angle of grinding and the width to which the face of the cutting edge is ground. One hand is used for drawing the knife through the machine, the other hand operates the handle for moving said blade supporting means, which handle is provided at a Fatented Oct. 9, 1956 place remote from the grinding station for safetys sake, while the manner in which said handle is actuated is the same for both grinding discs.

In order to accommodate different types of knives various types of blade supporting means may be used with the machine according to the invention. Owing to the stable built of said means and of the machine it is possible also to grind very thin, flexible, long or short knives at a minimum of expense and in a short time.

By replacing the grinding discs by polishing discs the machine may be converted into a polishing machine which operates on the same principles.

The invention is described hereinafter with reference to the accompanying drawings showing an embodiment of the machine according to the invention.

Figure 1 shows a front view of the machine and partly a section thereof.

Fig. 2 shows a side view of the machine.

Fig. 3 is a section through the carrying beam carrying a movable carriage with an adjusting disc and guide means.

Fig. 4 is a front-view of a blade supporting bridge mounted on the machine.

Fig. 5 is a front-view of a carriage provided with blade supporting means, which carriage is mounted for movement on the blade supporting bridge.

Fig. 6 is a section of said carriage.

In the drawing the reference numeral 1 designates a motor mounted on a foundation plate 2. On top of the motor 1 'a double grinding machine is provided, the left hand part 3 of which carries a grinding disc 4 which is driven by the motor 1 via a belt 5. The right hand part 6 carries a grinding disc 7 which is coplanar with the disc and is driven via the left hand part 3 by means of a crossed belt 8. As appears from the arrows the two discs rotate in opposite directions. On the foundation plate 2 a yoke 9 provided with a carrying beam 10 is mounted in a plane parallel to the plane of the grinding discs. On the yoke a and within the carrying beam 10 an actuating device 11 comprising a screw spindle provided with left hand and right hand thread is mounted. By means of the device 11 the two carriages 12 and 13 may be moved symmetrically relative to the grinding discs. In a plane parallel to the grinding discs pivotable adjusting discs 14 and 15 are mounted on said carriages. By means of an adjusting device comprising a shaft 16 and worms 18 and 1% said adjusting discs may be turned by operating a hand wheel 17, the movement of said discs being again symmetrical relative to the grinding discs. In guiding sleeves 2t and 21 secured to the adjusting discs 14 and 15 guide means 22 and 23 which are not rotatable, but which are longitudinally slidable, are provided. Said guide means may be moved up and down by means of a handle 24 which is hinged to the foundation plate 2 in journals 26 and 27 and which is provided with a roller 25 supporting the guide means 22 and 23 in opposition to spring pressure.

On the guide means 22 and 23 the various blade supporting means are secured with the help of screws 28 and 29. In case pointed knives or knives having varying cutting edge faces are to be ground the blade supports 30 and 31 are mounted on the guide means. By means of the actuating device 11 and the adjusting device 16-19 the knife supports 30 and 31 are brought in a grinding position adapted to the shape of the knife. The blade supports 30 and 31 each have two cutting edge supports 32, 33 and 34-, 35 which extend on either side of the grinding disc and which limit the movement of the blade towards the grinding discs, the grinding discs extending between the cutting edge supports over a dis-,

tance corresponding to the extent to which the blades are to be ground.

At the rear of the blade supports two supports for the back of a blade 36, 37 and 38, 39 are provided, said supports form the points of support for a blade to be ground and together with the grinding disc they provide the three-point support. Owing to the position of the cutting edge supports and the supports for the back of a blade the section of the knife as it were forms a hypotenuse of a triangle. In the case of a knife having a cross-section varying in its longitudinal direction the cutting edge to be ground is kept at the desired height by means of the handle 24, the cutting edge face to be ground being adapted to said cross-section. The blade first has its one side ground, the shape of the blade being followed by moving the handle and thereupon the blade is transferred to the other blade support for having its other side ground.

When a large number of knives having cutting edge faces that are uniform over the entire length of the blade is to be rapidly ground the blade supports 30 and 31 are replaced by a blade supporting bridge 40. Said bridge is secured to the guide means 22 and 23 by means of the screws 28 and 29 and may be vertically moved by means of the handle 24. The blade supporting bridge 40 is provided with a slot through which the grinding discs may pass and with two legs constructed as stationary rods or as longitudinal rollers, which rods or rollers flank the grinding discs.

A knife is then laid on the blade supporting bridge 40 and drawn along each of the grinding discs for sharpening both cutting edge faces. In order to obtain cutting edge faces of constant width the handle 24 is secured from movement in the journals 26 and 27 by means of clamping screws 41 and 42, the legs of the bridge serving then as cutting edge supports and at the same time as supports for the back of the blade. This arrangement is very suitable for rapidly whetting table knives. Part of the grinding force, however, is then taken up by the grinders hand. In case knives having very large cutting edge faces or capricious shapes are to be ground a carriage 43 is arranged on the blade supporting bridge 40. Said carriage may be moved across the bridge in the plane of the grinding discs by means of a handle 44, in this case a hand wheel, and a string 45. On the carriage a blade support 46 having four adjusting pins 47 at its corners, is secured, said blade support bearing on four compression springs 48 arranged about said adjusting pins. On either side of the grinding discs supports 49 for the back of the blade are again provided on the blade support 46, two on each side. The cutting edge supports are formed by two longitudinal rollers 50 and 51 which in the grinding position will lie besides the grinding discs.

The knife to be ground is now drawn along the grinding disc over the rollers 50 and 51 after the blade supporting bridge has been adjusted to the correct height by means of the handle 24, which handle is then secured from movement by means of the clamping screws 41 and 42. The supports for the back of the blade will urge the cutting edge thereof against the grinding disc. The position of the supports for the back of the blade is adapted to the width of the knife by means of the hand wheel 44. Owing to the stable construction and the controlled movement of the blade supports it is not diflicult to obtain hollow ground blades. In case a grinding disc exerts too great a pressure on a blade the blade and the blade support will be moved downwardly in opposition to the springs 48, so that the blade will not be damaged.

Because the grinding discs rotate from the cutting edge towards the back of the blade wire edges will not form while it is substantially impossible for the cutting edge to sag owing to the provision of the supporting means which flank the grinding discs. For safetys sake the means for driving the grinding discs are enclosed in a casing, while at the same time a hood is provided for exhausting the dust resulting from the grinding operation by means of a suction fan driven by the motor 1. These constructions have not been shown, because they are wellknown.

I claim:

1. A machine for sharpening the cutting edges of blades having varying edge contours comprising, in combination, two grinding discs mounted on parallel axial shafts projecting from one side of the discs, driving means for rotating one of the discs in clockwise direction and the other of the discs in counterclockwise direction, means supporting said discs in a common plane at a distance between the axes thereof greater than the sum of the radii of the discs, whereby the peripheries of the two discs are spaced apart, vertically adjustable blade supporting means for holding a knife against one of said grinding discs at a time, said supporting means having supporting surfaces lying in a plane which is at right angles to the plane of the discs and intersecting therewith along two lines spaced apart a distance greater than the radius of one the grinding discs whereby to form two different spaced-apart sharpening areas for the blade to permit the two faces of the blade to be ground successively by motion of the blade from one sharpening area to the other, the blade supporting means permitting one face of the blade to be manually pressed against the supporting means while leaving the other face directly visible to the operator.

2. A machine as defined in claim 1, wherein the vertically-adjustable blade supporting means comprises two spaced-apart shafts each disposed at the outer side of a grinding disc opposite said axial shafts, said spaced-apart shafts being mounted in guiding sleeves and being slidably movable in a plane parallel to the plane of the front face of the discs, spring means normally urging said shafts in one direction and actuating means common for both shafts for urging said shafts in the opposite direction.

3. A machine as defined in claim 2, wherein the common actuating means for the shafts comprise a horizontal bar passing under the lower ends of both shafts and a U-shaped lever bar having leg ends actuating said horizontal bar, the base of the U passing along the front side of the machine and parallel to the disc faces.

4. A machine as defined in claim 2, further characterized in that the upper ends of the spaced-apart shafts each bears one end of a blade support which is common to both grinding discs and is provided with at least one slit, an edge of each disc extending into the slit of the blade hearing plane of the blade support.

5. A machine as defined in claim 2, wherein the upper ends of the shaft each hear one end of a bridge and a blade support carriage is mounted slidably on said bridge for movement between the grinding discs.

6. A machine as defined in claim 1, wherein the bladesupporting means comprises protruding rests adapted to retain the back of a blade manually pressed upon the supporting means when the edge of the blade to be sharpened lies against the peripheral surface of one of the discs.

References Cited in the file of this patent UNITED STATES PATENTS 

